iPhone 6s is stuck in boot loop after battery replacement.

My iphone 6s had a bad battery when I bought it from one of my friends. I was aware of it too but was just looking for a backup phone. One day my 6s just stopped charging and eventually died. Tried multiple cables to see if maybe it was just a bad cable even tho they all worked with my Xr. Eventually I just bought a battery and replaced it. It started up and worked but wouldnt charge again. So I got the charger port replaced. After I was finished It started charging but got stuck in a boot loop. The battery holds a charge even when unplugged the phone still does it till I force the buttons down to force shut down and then it turn on and do the same thing till u force it off fast enough it stays off. Couldn’t figure out really what to do abt it at this point.